This epidemiological study will extend observations on about 50,000 former students from Harvard and the University of Pennsylvania to identify host and environmental characteristics in youth that predispose to specific chronic diseases later in life. Case-taking and other college records of the years 1916-1950 provide the initial documented data that are examined for associations with subsequent nonfatal and fatal diseases measured through self-administered questionnaires and death certificate information. Characteristics to be examined for their association with chronic diseases include familial, physical, sociocultural, and psychological traits. Chronic diseases for study will include site-specific cancers, respiratory disease, coronary heart disease, neurosensory disease, suicide and accidental death, peptic ulcer, and other chronic ailments. University alumni activities afford current addresses to facilitate identification of former students for morbidity projects and provide lists of deceased former students for mortality projects. Pathological changes underlying many chronic diseases begin in early childhood and are influenced by personal factors and habits of living that exert their force over long periods prior to the clinical recognition of disease. Use of predocumented data on adolescents and young adults, with followup observations on chronic diseases using college alumni facilities, compresses time and operational expenses into workable units. A better understanding or precursive elements in the days of youth is essential to reduce the incidence and temper the complications of chronic diseases later in life.